The group extraction of noble metals with s-(1-decyl)-N,N'-diphenylisothiouronium bromide and their determination in the organic extract by atomic-absorption spectrometry

The distribution coefficients are given for the noble metals and associated base metals between S-(1-decyI)-N, N'-diphenylisothiouronium (DDTU) in diisobutyl ketone and aqueous solutions containing varying molarities of hydrochloric acid. DDTU is a satisfactory reagent for the extraction of noble metals as a group from most of the associated base metals. Base metals such as iron(III), tin(II), and selenium(IV), which are co-extracted, can be removed from the organic phase by washing with 0.1 M hydrochloric acid; this affects only the recovery of iridium. Although the noble metals cannot be recovered from the organic phase by back-extraction, direct measurement in the organic phase is possible in ths presence of zinc dibenzyldithiocarbamate added as a releasing agent. The final solution for analysis contains 6 mg of additive per 10 ml of solution.